Effects of dietary β-1,3-glucan and host gut-derived probiotic bacteria on hemato-immunological indices and gut microbiota of juvenile rainbow trout (Oncorhynchus mykiss)

The effects of indigenous probiotics Lactobacillus plantarum and Lactobacillus pentosus alone, and in combination with β-1,3-glucan in juvenile rainbow trout (Oncorhynchus mykiss) were investigated. Eight groups were defined: control (G1), 1% β-1,3-glucan (G2), L. plantarum (G3), L. pentosus (G4), L. plantarum + L. pentosus (G5), L. plantarum with 1% β-1,3-glucan (G6), L. pentosus with 1% β-1,3-glucan (G7) and L. plantarum + L. pentosus with 1% β-1,3-glucan (G8). After eight weeks, the innate immune responses were elevated in all treated groups; however, synergistic effects were observed for anti-trypsin, bactericidal activity and respiratory burst activity in groups 7 and 8. Although the other immune responses were higher in treated groups, they did not make statistically significant differences. Checking microbiota showed that β-1,3-glucan improved conditions of indigenous probiotics. The diet 8 caused significant alterations in the intestinal microbiota by significantly decreasing the proportion of total count bacteria to lactic acid bacteria, which were demonstrated by reducing the total number of bacteria in Group 8 compared to the control group.